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I think Synch and White are the wrong way round in that sound test program. Can anyone confirm?
(I'm guessing Synch is meant to sound like buzzing, and White like hissing.)

Maxim, can you do the test with Channel 2's volume at F? Otherwise the tone gets mixed in. That's probably the weird stuff you saw in the WAV file.

Also, can you get recordings of the low mid and high versions of the Hiss noise? (Though it seems to be labelled "Synch" in the sound test.)

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> I think Synch and White are the wrong way round in that sound test program. Can anyone confirm?
> (I'm guessing Synch is meant to sound like buzzing, and White like hissing.)

I may have to wrong version posted.
I'll check on that this evening. The version that I do all my testing with has them the right way.
Another thing that's relevant, is that I think the version I posted updates the sound registers once a frame - I don't know if doing that resets some kind of shift register, I don't think it would on hardware, but I remember at least one emulator had weird sounding noise in my sound test because of it.

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> Maxim, can you do the test with Channel 2's volume at F? Otherwise the tone gets mixed in. That's probably the weird stuff you saw in the WAV file.

I think that was intentional, you can count how many PSG cycles elapse between noise pulses. (so actual frequency settings become irrelevant.. or should become irrelevant.)

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> Also, can you get recordings of the low mid and high versions of the Hiss noise? (Though it seems to be labelled "Synch" in the sound test.)

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> I think Synch and White are the wrong way round in that sound test program. Can anyone confirm?
> (I'm guessing Synch is meant to sound like buzzing, and White like hissing.)

The synch noise sounds synchronous to me (I can hear a repeat in it), the white doesn't. So I think they're right.

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> Maxim, can you do the test with Channel 2's volume at F? Otherwise the tone gets mixed in. That's probably the weird stuff you saw in the WAV file.

Like Heliophobe said, it's on purpose, so you can see the shift triggers.

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> Also, can you get recordings of the low mid and high versions of the Hiss noise? (Though it seems to be labelled "Synch" in the sound test.)

Already done that :) Old sound test stuff which I did when I got my hands on a devcart and an SMSReader(/Writer).

Maxim

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> Another thing that's relevant, is that I think the version I posted updates the sound registers once a frame - I don't know if doing that resets some kind of shift register, I don't think it would on hardware, but I remember at least one emulator had weird sounding noise in my sound test because of it.

Can you make a version that doesn't? Maybe have Pause toggle the write every frame. I think this might be causing strange results... I hereby command everyone to disregard all previous samples of noise until this is sorted out...

Maxim

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> Can you make a version that doesn't? Maybe have Pause toggle the write every frame. I think this might be causing strange results... I hereby command everyone to disregard all previous samples of noise until this is sorted out...

Right, I have a version at home that doesn't do that, I just didn't bother posting it.

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> > Can you make a version that doesn't? Maybe have Pause toggle the write every frame. I think this might be causing strange results... I hereby command everyone to disregard all previous samples of noise until this is sorted out...

> Right, I have a version at home that doesn't do that, I just didn't bother posting it.

It seems it does reset the shift register. A bit of simple arithmetic finds...

Low frequency noise is tuned to PSG value 0x040. On a PAL SMS this comes out at 1731Hz.

At 50 frames per second, we have 34.64 cycles per frame. So, sometimes there will be 34 cycles between writes, sometimes 35.

Looking at the data I had... there were gap lengths of 15 then 18, or 15 then 17. 1+15+1+18 = 35, 1+15+1+17 = 34.

So, something to add to the docs: PSG noise writes reset the shift register. Maybe adding this will make noise sound better? I already tried it in my plugin and it sounds much the same.

Maxim

Sorry to have rendered all your tests completely useless. But then, we might not have realized a change to the noise register resets the shift if it weren't for that.

Forgot to upload it, dang. Actually, I think I've got the source here at work still, maybe I can fix it now.. um, haven't done any z80 stuff in nearly half a year, let's see if I'm still any good at it.

Author	Message
Dave Guest	Noise in Sound test Posted: Wed Aug 15, 2001 8:45 pm
Dave Guest	I think Synch and White are the wrong way round in that sound test program. Can anyone confirm? (I'm guessing Synch is meant to sound like buzzing, and White like hissing.) Maxim, can you do the test with Channel 2's volume at F? Otherwise the tone gets mixed in. That's probably the weird stuff you saw in the WAV file. Also, can you get recordings of the low mid and high versions of the Hiss noise? (Though it seems to be labelled "Synch" in the sound test.)

Heliophobe Site Admin Joined: 25 Oct 1999 Posts: 2029 Location: Monterey, California	Posted: Wed Aug 15, 2001 8:57 pm
	Quote > I think Synch and White are the wrong way round in that sound test program. Can anyone confirm? > (I'm guessing Synch is meant to sound like buzzing, and White like hissing.) I may have to wrong version posted. I'll check on that this evening. The version that I do all my testing with has them the right way. Another thing that's relevant, is that I think the version I posted updates the sound registers once a frame - I don't know if doing that resets some kind of shift register, I don't think it would on hardware, but I remember at least one emulator had weird sounding noise in my sound test because of it. Quote > Maxim, can you do the test with Channel 2's volume at F? Otherwise the tone gets mixed in. That's probably the weird stuff you saw in the WAV file. I think that was intentional, you can count how many PSG cycles elapse between noise pulses. (so actual frequency settings become irrelevant.. or should become irrelevant.) Quote > Also, can you get recordings of the low mid and high versions of the Hiss noise? (Though it seems to be labelled "Synch" in the sound test.)

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14749 Location: London	Posted: Wed Aug 15, 2001 9:59 pm
	Quote > I think Synch and White are the wrong way round in that sound test program. Can anyone confirm? > (I'm guessing Synch is meant to sound like buzzing, and White like hissing.) The synch noise sounds synchronous to me (I can hear a repeat in it), the white doesn't. So I think they're right. Quote > Maxim, can you do the test with Channel 2's volume at F? Otherwise the tone gets mixed in. That's probably the weird stuff you saw in the WAV file. Like Heliophobe said, it's on purpose, so you can see the shift triggers. Quote > Also, can you get recordings of the low mid and high versions of the Hiss noise? (Though it seems to be labelled "Synch" in the sound test.) Already done that :) Old sound test stuff which I did when I got my hands on a devcart and an SMSReader(/Writer). Maxim

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14749 Location: London	Posted: Wed Aug 15, 2001 10:32 pm
	Quote > Another thing that's relevant, is that I think the version I posted updates the sound registers once a frame - I don't know if doing that resets some kind of shift register, I don't think it would on hardware, but I remember at least one emulator had weird sounding noise in my sound test because of it. Can you make a version that doesn't? Maybe have Pause toggle the write every frame. I think this might be causing strange results... I hereby command everyone to disregard all previous samples of noise until this is sorted out... Maxim

Heliophobe Site Admin Joined: 25 Oct 1999 Posts: 2029 Location: Monterey, California	Posted: Wed Aug 15, 2001 10:35 pm
	Quote > Can you make a version that doesn't? Maybe have Pause toggle the write every frame. I think this might be causing strange results... I hereby command everyone to disregard all previous samples of noise until this is sorted out... Right, I have a version at home that doesn't do that, I just didn't bother posting it.

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14749 Location: London	Re: Noise in Sound test - officially broken Posted: Thu Aug 16, 2001 9:35 am
	Quote > > Can you make a version that doesn't? Maybe have Pause toggle the write every frame. I think this might be causing strange results... I hereby command everyone to disregard all previous samples of noise until this is sorted out... > Right, I have a version at home that doesn't do that, I just didn't bother posting it. It seems it does reset the shift register. A bit of simple arithmetic finds... Low frequency noise is tuned to PSG value 0x040. On a PAL SMS this comes out at 1731Hz. At 50 frames per second, we have 34.64 cycles per frame. So, sometimes there will be 34 cycles between writes, sometimes 35. Looking at the data I had... there were gap lengths of 15 then 18, or 15 then 17. 1+15+1+18 = 35, 1+15+1+17 = 34. So, something to add to the docs: PSG noise writes reset the shift register. Maybe adding this will make noise sound better? I already tried it in my plugin and it sounds much the same. Maxim

Heliophobe Site Admin Joined: 25 Oct 1999 Posts: 2029 Location: Monterey, California	Well, at least we learned something Posted: Thu Aug 16, 2001 5:51 pm
	Sorry to have rendered all your tests completely useless. But then, we might not have realized a change to the noise register resets the shift if it weren't for that. Forgot to upload it, dang. Actually, I think I've got the source here at work still, maybe I can fix it now.. um, haven't done any z80 stuff in nearly half a year, let's see if I'm still any good at it.

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